Methods and Compositions Comprising Cement Kiln Dust Having an Altered Particle Size

ABSTRACT

Methods and compositions are disclosed that comprise cement kiln dust having a mean particle size that has been altered. An embodiment discloses a method of preparing cement kiln dust comprising: providing cement kiln dust having an original particle size; and altering the mean particle size of the cement kiln dust from the original size by grinding, separating, or a combination thereof. Another embodiment discloses a well treatment fluid comprising: cement kiln dust having a mean particle size that has been altered from its original size by grinding, separating, or a combination thereof; and water.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/399,913, entitled “Methods and Compositions Comprising Cement KilnDust Flaying an Altered Particle Size,” filed on Feb. 17, 2012, which isa continuation in part of U.S. patent application Ser. No. 13/180,238,entitled “Settable Compositions Comprising Interground Perlite andHydraulic Cement,” filed on Jul. 11, 2011, which is acontinuation-in-part of U.S. patent application Ser. No. 12/975,196,entitled “Settable Compositions Comprising Unexpanded Perlite andMethods of Cementing in Subterranean Formations,” filed on Dec. 21,2010, the entire disclosures of which are incorporated herein byreference. U.S. patent application Ser. No. 13/399,913, entitled“Methods and Compositions Comprising Cement Kiln Dust Having an AlteredParticle Size,” filed on Feb. 17, 2012, is also a continuation-in-partof U.S. patent application Ser. No. 12/895,436, entitled “Spacer FluidsContaining Cement Kiln Dust and Methods of Use, filed on Sep. 30, 2010,which is a continuation-in-part of U.S. patent application Ser. No.12/264,010, entitled “Reduced Carbon Footprint Settable Compositions forUse in Subterranean Formations,” filed on Nov. 3, 2008, which is acontinuation-in-part of U.S. patent application Ser. No. 11/223,669,issued as U.S. Pat. No. 7,445,669, entitled “Settable CompositionsComprising Cement Kiln Dust and Additive(s),” filed Sep. 9, 2005, theentire disclosures of which are incorporated herein by reference.

BACKGROUND

In general, well treatments include a wide variety of methods that maybe performed in oil, gas, geothermal and/or water wells, such asdrilling, completion and workover methods. The drilling, completion andworkover methods may include, but are not limited to, drilling,fracturing, acidizing, logging, cementing, gravel packing, perforatingand conformance methods. Many of these well treatments are designed toenhance and/or facilitate the recovery of desirable fluids from asubterranean well.

In cementing methods, such as well construction and remedial cementing,settable compositions are commonly utilized. As used herein, the term“settable composition” refers to a composition(s) that hydraulicallysets or otherwise develops compressive strength. Settable compositionsmay be used in primary cementing operations whereby pipe strings, suchas casing and liners, are cemented in well bores. In performing primarycementing, a settable composition may be pumped into an annulus betweena subterranean formation and the pipe string disposed in thesubterranean formation. The settable composition should set in theannulus, thereby forming an annular sheath of hardened cement (e.g., acement sheath) that should support and position the pipe string in thewell bore and bond the exterior surface of the pipe string to the wallsof the well bore. Settable compositions also may be used in remedialcementing methods, such as the placement of cement plugs, and in squeezecementing for sealing voids in a pipe string, cement sheath, gravelpack, formation, and the like. Settable compositions may also be used insurface applications, for example, construction cementing.

Settable compositions for use in subterranean formations may furtherinclude Portland cement. Portland cement generally is a major componentof the cost for the cement compositions. Other components may beincluded in the cement composition in addition to, or in place of, thePortland cement. Such components may include fly ash, slag, shale,zeolite, metakaolin, pumice, perlite, lime, silica, rice-hull ash,micro-fine cement, lime kiln dust, and the like. However, the operatingconditions for wells are becoming more challenging and demanding, andthe search for new materials continues to meet these challenges.

SUMMARY

An embodiment discloses a subterranean treatment method. The method maycomprise introducing a treatment fluid into a subterranean formation,wherein the treatment fluid comprises cement kiln dust having a meanparticle size that has been altered from its original size by grinding,separating, or a combination thereof.

Another embodiment discloses a subterranean treatment method. The methodmay comprise introducing a treatment fluid into a subterraneanformation, wherein the treatment fluid comprises cement kiln dust havinga mean particle size that has been reduced from its original size.

Another embodiment discloses a subterranean treatment method. The methodmay comprise introducing a treatment fluid into a subterraneanformation, wherein the treatment fluid comprises cement kiln dust thathas been ground.

Another embodiment discloses a method of preparing cement kiln dust. Themethod may comprise providing cement kiln dust having an originalparticle size. The method may further comprise altering the meanparticle size of the cement kiln dust from the original particle size bygrinding, separating, or a combination thereof.

Another embodiment discloses a well treatment fluid. The well treatmentfluid may comprise cement kiln dust having a mean particle size that hasbeen altered from its original particle size by grinding, separating, ora combination thereof.

Another embodiment discloses an additive for a settable composition. Theadditive may comprise cement kiln dust having a mean particle size thathas been altered from its original particle size by grinding,separating, or a combination thereof.

The features and advantages of the present invention will be readilyapparent to those skilled in the art. While numerous changes may be madeby those skilled in the art, such changes are within the spirit of theinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the settable compositions of the present inventioncomprise cement kiln dust having a mean particle size that has beenaltered from its original size. The mean particle size of the cementkiln dust may be altered, for example, to selectively increase ordecrease the mean particle size as desired for a particular application.

In embodiments of the present invention, altering the mean particle sizeof the cement kiln dust may improve one or more properties of the cementkiln dust, including the void-filling properties, gelation times, andcompressive strengths. In some embodiments, the mean particle size ofthe cement kiln dust may be selectively altered based on the sizes ofvoids to be filled, which may be beneficial in remedial cementingmethods, for example. For example, the mean particle size of the cementkiln dust may be optimized to more effectively fill voids in a pipestring, cement sheath, gravel pack, formation, or the like. In someembodiment, it is believed that altering the mean particle size of thecement kiln dust may be used to adjust the gelation time of compositionscontaining the cement kiln dust. In some embodiments, the mean particlesize of the cement kiln dust may be reduced to provide an increase incompressive strength. For example, reducing mean particle size of thecement kiln dust to less than about 15 microns has been shown to provideunexpected increases in compressive strength for settable compositionsto which the cement kiln dust may be added, especially when compared touse of the cement kiln dust prior to the size reduction.

In some embodiments, the mean particle size of the cement kiln dust maybe reduced from its original size to provide an increase in compressivestrength of at least about 5%, for example an increase in an amount in arange of at least about 5% to about 100%. In specific embodiments, themean particle size of the cement kiln dust may be reduced to provide anincrease in compressive strength of at least about 20%, at least about40%, at least about 60%, at least about 80%, or at least about 100%. Itshould be understood that, as used herein, an increase in compressivestrength for the cement kiln dust having a reduced mean particle sizerefers to a comparison of the compressive strength of a settablecomposition comprising the reduced particle size cement kiln dust to asettable composition comprising the original cement kiln dust prior tothe particle size reduction. The compressive strength may be determinedusing either a destructive or non-destructive testing method. In someembodiments, the compressive strength tests may be performed inaccordance with API RP Practice 10B-2, Recommended Practice for TestingWell Cements, First Edition, July 2005. For example, the 24-hourcompressive strength for a settable composition comprising the cementkiln dust may be determined using an Ultrasonic Cement Analyzer fromFarm Instruments, Houston, Tex., while maintained at 140° F. and 8,000pounds per square inch (“psi”). In one particular example, the 24-hourcompressive strengths may be determined for a settable compositionhaving a density of about 12 pounds per gallon (“lb/gal”).

Cement kiln dust, as that term is used herein, refers to a partiallycalcined kiln feed which is removed from the gas stream and collected,for example, in a dust collector during the manufacture of cement. Thecement kiln dust generally may exhibit cementitious properties, in thatit may set and harden in the presence of water. Usually, largequantities of cement kiln dust are collected in the production of cementthat are commonly disposed of as waste. Disposal of the cement kiln dustcan add undesirable costs to the manufacture of the cement, as well asthe environmental concerns associated with its disposal. The chemicalanalysis of the cement kiln dust from various cement manufactures variesdepending on a number of factors, including the particular kiln feed,the efficiencies of the cement production operation, and the associateddust collection systems. Cement kin dust generally may comprise avariety of oxides, such as SiO₂, Al₂O₃, Fe₂O₃, CaO, MgO, SO₃, Na₂O, andK₂O.

In accordance with present embodiments, the mean particle size of thecement kiln dust can be altered using any suitable technique, including,without limitation, grinding or separating to provide a material havingan altered particle size. Separating the cement kiln dust may includesieving or any other suitable technique for separating the cement kilndust to provide a mean particle size that has been altered from itsoriginal size. For example, sieving may be used to produce cement kilndust having an increased or reduced mean particle size as desired for aparticular application. By way of further example, grinding may be usedto decrease the mean particle size of the cement kiln dust. Combinationsof grinding and separating may be used in some embodiments. The term“ground” or “grinding” as used herein means using a grinder (e.g., ballmill, rod mill, etc.) to reduce the particle size of the specifiedcomponent(s). An example of a suitable grinder is an 8000 Mixer/Mill®ball mill, available from SPEX Sample Prep. In some embodiments, thecement kiln dust may be ground for a time period in a range of fromabout 30 minutes to about 1 hour.

The mean particle size of the cement kiln dust can be altered to anysize suitable for use in cementing operations. In some embodiments, themean particle size of the cement kiln dust may be altered from itsoriginal particle size to have a mean particle size in a range of about1 micron to about 350 microns. The mean particle size corresponds to d50values as measured by particle size analyzers such as those manufacturedby Malvern Instruments, Worcestershire, United Kingdom.

In some embodiments, the mean particle size of the cement kiln of thecement kiln dust may be increased from its original size. For example,the mean particle size of the cement kiln dust may be at least 5%greater than its original size. In some embodiments, at least a portionof the cement kiln dust may be increased to a size that is in a range offrom about 5% to about 100% greater than its original size. In someembodiments, the mean particle size may be increased to a size rangingbetween any of and/or including any of about 5%, about 10%, about 15%,about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%,about 90%, or about 95% greater than its of the original size.

In some embodiments, the mean particle size of the cement kiln dust maybe reduced from its original size. For example, the mean particle sizemay be reduced in an amount sufficient to increase the compressivestrength of the cement kiln dust. In some embodiments, the cement kilndust may have a mean particle size that is at least 5% less than itsoriginal size. In some embodiments, at least a portion of the cementkiln dust may be reduced to have a mean particle size in a range of fromabout 5% to about 95% of its original size. For example, the meanparticle size may be reduced to a size ranging between any of and/orincluding any of about 5%, about 10%, about 15%, about 20%, about 25%,about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about60%, about 6%, about 70%, about 75%, about 80%, about 90%, or about 95%of its original size. By way of example, the reduced particle sizecement kiln dust may have a mean particle size of less than about 15microns. In some embodiments, the reduced particle size cement kiln dustmay have a mean particle size of less than about 10 microns, less thanabout 5 microns, less than about 4 microns, less than about 3 microns,less than about 2 microns, or less than about 1 micron. In specificembodiments, the reduced particle size cement kiln dust may have a meanparticle size in a range of from about 0.1 microns to about 15 microns,from about 0.1 microns to about 10 microns, or from about 1 micron toabout 10 microns. One of ordinary skill in the art, with the benefit ofthis disclosure, should be able to select a particle size for the cementkiln dust suitable for a particular application.

The cement kiln dust having a particle size that has been altered may beincluded in the settable compositions in an amount sufficient toprovide, for example, the desired compressive strength, gelation time,and the like. In some embodiments, the altered particle size cement kilndust may be present in the settable compositions of the presentinvention in an amount in the range of from about 1% to 100% by weightof cementitious components (“% bwoc”). The term “cementitiouscomponents” refers to the components, or a combination thereof, of thesettable compositions that hydraulically set, or otherwise harden, todevelop compressive strength, including, for example, cement kiln dust,Portland cement, fly ash, natural pozzolans (e.g., pumicite), slag,lime, shale, and the like. The altered particle size cement kiln dustmay be present in an amount, for example, ranging between any of and/orincluding any of about 5%, about 10%, about 15%, about 20%, about 25%,about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about60%, about 65%, about 70%, about 75%, about 80%, about 90%, about 95%,or 100% bwoc. In specific embodiments, the altered particle size cementkiln dust may be present in the settable compositions in an amount inthe range of from about 5% to 100% bwoc, from about 50% to 100% bwoc, orfrom about 75% to 100% bwoc. One of ordinary skill in the art, with thebenefit of this disclosure, will recognize the appropriate amount of thecement kiln dust having a mean particle size that has been altered toinclude for a chosen application.

Embodiments of the settable compositions may further comprise one ormore additional additives, including, but not limited to, hydrauliccement, fly ash, slag, shale, zeolite, metakaolin, pumice, perlite,lime, silica, rice-hull ash, micro-fine cement, lime kiln dust, andcombinations thereof, and the like. In accordance with presentembodiments, the cement kiln dust having a mean particle size that hasbeen altered may be prepared by a process comprising intergrinding thecement kiln dust with one or more of the additional additives to aparticular desired size. For example, the cement kiln dust and the oneor more additional additives may be interground to a mean particle sizeof less than about 15 microns. In some embodiments, the cement kiln dustand the one or more additional additives may be interground to a meanparticle size of less than about 10 microns, less than about 5 microns,less than about 4 microns, less than about 3 microns, less than about 2microns, or less than about 1 micron. In specific embodiments, thecement kiln dust and the one or more additional additives may beinterground to a mean particle size in a range from about 0.1 microns toabout 15 microns, from about 0.1 microns to about 10 microns, or fromabout 1 micron to about 10 microns. One of ordinary skill in the art,with the benefit of this disclosure, should be able to select a particlesize of the interground cement kiln dust and the one or more additionaladditives suitable for a particular application.

Hydraulic cement may be included in embodiments of the settablecompositions of the present invention. A variety of hydraulic cementsmay be utilized in accordance with the present invention, including, butnot limited to, those comprising calcium, aluminum, silicon, oxygen,iron, and/or sulfur, which set and harden by reaction with water.Suitable hydraulic cements include, but are not limited to, Portlandcements, pozzolana cements, gypsum cements, high alumina contentcements, slag cements, silica cements, and combinations thereof. Incertain embodiments, the hydraulic cement may comprise a Portlandcement, including Portland cements classified as Classes A, C, G and Hcements according to American Petroleum Institute, API Specification forMaterials and Testing for Well Cements, API Specification 10, FifthEdition, Jul. 1, 1990. In addition, Portland cements suitable for use inembodiments the present invention may also include those classified asASTM Type I, II, III, IV, or V. In some embodiments, the cement may bepresent in the settable compositions in an amount in the range of fromabout 0.1% to about 99% bwoc. For example, the cement may be present inan amount ranging between any of and/or including any of about 5%, about10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%,about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about75%, about 80%, about 85%, about 90%, or about 95% bwoc. One of ordinaryskill in the art, with the benefit of this disclosure, will recognizethe appropriate amount of the cement to include for a chosenapplication.

Fly ash may be included in embodiments of the settable compositions ofthe present invention. A variety of fly ashes may be suitable, includingfly ash classified as Class C and Class F fly ash according to AmericanPetroleum Institute, API Specification for Materials and Testing forWell Cements, API Specification 10, Fifth Ed., Jul. 1, 1990. Class C flyash comprises both silica and lime so that, when mixed with water, itsets to form a hardened mass. Class F fly ash generally does not containsufficient lime, so an additional source of calcium ions may be requiredfor the Class F fly ash to form a settable composition with water. Insome embodiments, lime may be mixed with Class F fly ash in an amount inthe range of about 0.1% to about 25% by weight of the fly ash. In someinstances, the lime may be hydrated lime. Suitable examples of fly ashinclude, but are not limited to, POZMIX® A cement additive, availablefrom Halliburton Energy Services, Inc., Duncan, Okla. Where present, thefly ash generally may be included in the settable compositions in anamount sufficient to provide the desired compressive strength, density,and/or cost. In some embodiments, the fly ash may be present in settablecompositions of the present invention in an amount in the range of about0.1% to about 75% bwoc. In some embodiments, the fly ash may be presentin an amount ranging between any of and/or including any of about 10%,about 20%, about 30%, about 40%, about 50%, about 60%, or about 70%bwoc. One of ordinary skill in the art, with the benefit of thisdisclosure, will recognize the appropriate amount of the fly ash toinclude for a chosen application.

Slag may be included in embodiments of the settable compositions of thepresent invention. Slag generally does not contain sufficient basicmaterial, so slag may be used with a base to produce a settablecomposition that may react with water to set to form a hardened mass.Examples of suitable sources of bases include, but are not limited to,sodium hydroxide, sodium bicarbonate, sodium carbonate, lime, andcombinations thereof. Where present, the slag generally may be includedin the settable compositions in an amount sufficient to provide thedesired compressive strength, density, and/or cost. In some embodiments,the slag may be present in settable compositions of the presentinvention in an amount in the range of about 0.1% to about 75% bwoc. Insome embodiments, the slag may be present in an amount ranging betweenany of and/or including any of about 10%, about 20%, about 30%, about40%, about 50%, about 60%, or about 70% bwoc. One of ordinary skill inthe art, with the benefit of this disclosure, will recognize theappropriate amount of the slag to include for a chosen application.

Shale may be included in embodiments of the settable compositions of thepresent invention. A variety of shales may be suitable, including thosecomprising silicon, aluminum, calcium, and/or magnesium. An example of asuitable shale comprises vitrified shale. Suitable examples of vitrifiedshale include, but are not limited to, PRESSUR-SEAL FINE LCM materialand PRESSUR-SEAL COARSE LCM material, which are available from TXIEnergy Services, Inc., Houston, Tex. Generally, the shale may have anyparticle size distribution as desired for a particular application. Incertain embodiments, the shale may have a particle size distribution inthe range of about 37 microns to about 4,750 microns. Where present, theshale may be included in the settable compositions of the presentinvention in an amount sufficient to provide the desired compressivestrength, density, and/or cost. In some embodiments, the shale may bepresent in settable compositions of the present invention in an amountin the range of about 0.1% to about 75% bwoc. In some embodiments, theshale may be present in an amount ranging between any of and/orincluding any of about 10%, about 20%, about 30%, about 40%, about 50%,about 60%, or about 70% bwoc. One of ordinary skill in the art, with thebenefit of this disclosure, will recognize the appropriate amount of theshale to include for a chosen application.

Zeolite may be included in embodiments of the settable compositions ofthe present invention. Zeolites suitable for use typically may includeporous alumino-silicate minerals that may be either a natural orsynthetic material. Synthetic zeolites are based on the same type ofstructural cell as natural zeolites, and may comprise aluminosilicatehydrates. As used herein, the term “zeolite” refers to all natural andsynthetic forms of zeolite. Examples of suitable zeolites are describedin more detail in U.S. Pat. No. 7,445,669. An example of a suitablesource of zeolite is available from the C2C Zeolite Corporation ofCalgary, Canada. In some embodiments, the zeolite may be present insettable compositions of the present invention in an amount in the rangeof about 0.1% to about 75% bwoc. In some embodiments, the zeolite may bepresent in an amount ranging between any of and/or including any ofabout 10%, about 20%, about 30%, about 40%, about 50%, about 60%, orabout 70% bwoc. One of ordinary skill in the art, with the benefit ofthis disclosure, will recognize the appropriate amount of the zeolite toinclude for a chosen application.

Metakaolin may be included in embodiments of the settable compositionsof the present invention. Generally, metakaolin is a white pozzolan thatmay be prepared by heating kaolin clay, for example, to temperatures inthe range of about 600° C. to about 800° C. In some embodiments, themetakaolin may be present in settable compositions of the presentinvention in an amount in the range of about 0.1% to about 75% bwoc. Insome embodiments, the metakaolin may be present in an amount rangingbetween any of and/or including any of about 10%, about 20%, about 30%,about 40%, about 50%, about 60%, or about 70% bwoc. One of ordinaryskill in the art, with the benefit of this disclosure, will recognizethe appropriate amount of the metakaolin to include for a chosenapplication.

Pumice may be included in embodiments of the settable compositions ofthe present invention. Generally, pumice is a volcanic rock thatexhibits cementitious properties, in that it may set and harden in thepresence of hydrated lime and water. Hydrated lime may be used incombination with the pumice, for example, to provide sufficient calciumions for the pumicite to set. In some embodiments, the pumice may bepresent in settable compositions of the present invention in an amountin the range of about 0.1% to about 75% bwoc. In some embodiments, thepumice may be present in an amount ranging between any of and/orincluding any of about 10%, about 20%, about 30%, about 40%, about 50%,about 60%, or about 70% bwoc. One of ordinary skill in the art, with thebenefit of this disclosure, will recognize the appropriate amount of thepumice to include for a chosen application.

Perlite may be included in embodiments of the settable compositions ofthe present invention. Perlite is an ore and generally refers to anaturally occurring volcanic, amorphous siliceous rock comprising mostlysilicon dioxide and aluminum oxide. Perlite suitable for use inembodiments of the present invention includes expanded perlite andunexpanded perlite. In some embodiments, the perlite may compriseunexpanded perlite. The perlite may also be ground, for example. In someembodiments, the perlite may be present in settable competitions of thepresent invention in an amount in the range of about 0.1% to about 75%bwoc. In some embodiments, the perlite may be present in an amountranging between any of and/or including any of about 10%, about 20%,about 30%, about 40%, about 50%, about 60%, or about 70% bwoc. One ofordinary skill in the art, with the benefit of this disclosure, willrecognize the appropriate amount of the perlite to include for a chosenapplication.

Lime may be included in embodiments of the settable compositions of thepresent invention. In certain embodiments, the lime may be hydratedlime. The lime may be included in embodiments of the settablecompositions, for example to, form a hydraulic composition with othercomponents of the settable compositions, such as the pumice, fly ash,slag, and/or shale. Where present, the lime may be included in thesettable compositions in an amount in the range of from about 0.1% toabout 25% bwoc, for example. In some embodiments, the lime may bepresent in an amount ranging between any of and/or including any ofabout 5%, about 10%, about 15%, about 20%, or about 25% bwoc. One ofordinary skill in the art, with the benefit of this disclosure, willrecognize the appropriate amount of the lime to include for a chosenapplication.

Silica may be included in embodiments of the settable compositions ofthe present invention. Silicas suitable for use typically may includeamorphous silica, crystalline silica, or combinations thereof.Crystalline silica is a powder that may be included in embodiments ofthe settable compositions, for example, to prevent cement compressivestrength retrogression. Amorphous silica is a powder that may beincluded in embodiments of the settable compositions as a lightweightfiller and/or to increase cement compressive strength. In someembodiments, the silica may be present in settable compositions of thepresent invention in an amount in the range of about 0.1% to about 75%bwoc. In some embodiments, the silica may be present in an amountranging between any of and/or including any of about 10%, about 20%,about 30%, about 40%, about 50%, about 60%, or about 70% bwoc. One ofordinary skill in the art, with the benefit of this disclosure, willrecognize the appropriate amount of the silica to include for a chosenapplication.

Rice-hull ash may be included in embodiments of the settablecompositions of the present invention. In general, rice-hull ash is theash produced from the burning of rice hulls, which are the hardcoverings of grains of rice, and may comprise primarily silica andcarbon. In some embodiments, the rice-hull ash may be present insettable compositions of the present invention in an amount in the rangeof about 0.1% to about 75% bwoc. In some embodiments, the rice-hull ashmay be present in an amount ranging between any of and/or including anyof about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, orabout 70% bwoc. One of ordinary skill in the art, with the benefit ofthis disclosure, will recognize the appropriate amount of the rice-hullash to include for a chosen application.

Micro-fine cement may be included in embodiments of the settablecompositions of the present invention. As used herein, the term“micro-fine cement” refers to a cement having a mean particle size nolarger than about 5 microns, for example, in a range of about 1 micronto about 5 microns. In some embodiments, the micro-fine cement may bepresent in settable compositions of the present invention in an amountin the range of about 0.1% to about 75% bwoc. In some embodiments, themicro-fine cement may be present in an amount ranging between any ofand/or including any of about 10%, about 20%, about 30%, about 40%,about 50%, about 60%, or about 70% bwoc. One of ordinary skill in theart, with the benefit of this disclosure, will recognize the appropriateamount of the micro-fine cement to include for a chosen application.

Lime kiln dust may be included in embodiments of the settablecompositions of the present invention. Lime kiln dust, as that term isused herein, refers to a product generated in the manufacture of lime.The lime kiln dust may be collected, for example, by dust controlsystems in the calcination of lime stone. In some embodiments, the limekiln dust may be present in settable compositions of the presentinvention in an amount in the range of about 0.1% to about 75% bwoc. Insome embodiments, the lime kiln dust may be present in an amount rangingbetween any of and/or including any of about 10%, about 20%, about 30%,about 40%, about 50%, about 60%, or about 70% bwoc. One of ordinaryskill in the art, with the benefit of this disclosure, will recognizethe appropriate amount of the lime kiln dust to include for a chosenapplication.

Embodiments of the settable compositions further may include water. Thewater that may be used in embodiments of the settable compositionsinclude, for example, freshwater, saltwater (e.g., water containing oneor more salts dissolved therein), brine (e.g., saturated saltwaterproduced from subterranean formations), seawater, or combinationsthereof. Generally, the water may be from any source, provided that thewater does not contain an excess of compounds that may undesirablyaffect other components in the settable composition. In someembodiments, the water may be included in an amount sufficient to form apumpable slurry. In some embodiments, the water may be included in thesettable compositions of the present invention in an amount in the rangeof about 40% to about 200% bwoc. For example, the water may be presentin an amount ranging between any of and/or including any of about 50%,about 75%, about 100%, about 125%, about 150%, or about 175% bwoc. Inspecific embodiments, the water may be included in an amount in therange of about 40% to about 150% bwoc. One of ordinary skill in the art,with the benefit of this disclosure, will recognize the appropriateamount of water to include for a chosen application.

Optionally, other additional additives may be added to the settablecompositions of the present invention as deemed appropriate by oneskilled in the art, with the benefit of this disclosure. Examples ofsuch additives include, but are not limited to, strength-retrogressionadditives, set accelerators, weighting agents, lightweight additives,gas-generating additives, mechanical-property-enhancing additives,lost-circulation materials, filtration-control additives, dispersants,fluid-loss-control additives, defoaming agents, foaming agents,oil-swellable particles, water-swellable particles, thixotropicadditives, and combinations thereof. Specific examples of these, andother, additives include salts, fibers, hydratable clays, microspheres,elastomers, elastomeric particles, resins, latex, combinations thereof,and the like. A person having ordinary skill in the art, with thebenefit of this disclosure, will readily be able to determine the typeand amount of additive useful for a particular application and desiredresult. Embodiments of the settable compositions may be foamed and/orextended as desired by those of ordinary skill in the art.

The settable compositions of the present invention should have a densitysuitable for a particular application as desired by those of ordinaryskill in the art, with the benefit of this disclosure. In someembodiments, the settable compositions may have a density in the rangeof from about 8 lb/gal to about 16 lb/gal. In other embodiments, thesettable compositions may be foamed to a density in the range of fromabout 8 lb/gal to about 13 lb/gal.

While the settable compositions may be suitable for a number ofdifferent cementing operations, they may be particularly suitable formethods of cementing in a subterranean formation. For example, thesettable compositions may be used in primary and remedial cementingoperations in which the settable compositions may be introduced into asubterranean formation and allowed to set. As used herein, introducing,the settable composition into a subterranean formation includesintroduction into any portion of the subterranean formation, including,without limitation, into a well bore drilled into the subterraneanformation, into a near well bore region surrounding the well bore, orinto both.

In primary cementing embodiments, for example, a settable compositionmay be introduced into a space between a wall of a well bore and aconduit (e.g., pipe strings, liners) located in the well bore, the wellbore penetrating the subterranean formation. The settable compositionmay be allowed to set to form an annular sheath of hardened cement inthe space between the well bore wall and the conduit. Among otherthings, the set settable composition may form a barrier, preventing themigration of fluids in the well bore. The set settable composition alsomay, for example, support the conduit in the well bore.

In remedial cementing embodiments, a settable composition may be used,for example, in squeeze-cementing operations or in the placement ofcement plugs. By way of example, the settable composition may be placedin a well bore to plug an opening, such as a void or crack, in theformation, in a gravel pack, in the conduit, in the cement sheath,and/or a microannulus between the cement sheath and the conduit.

While the preceding description is directed to the use of the cementkiln dust having a mean particle size that has been altered insubterranean cementing methods, it should be understood that embodimentsof the present technique also encompasses the use of the alteredparticle size cement kiln dust in any of a variety of differentsubterranean treatments. For example, a subterranean treatment methodmay include providing a treatment fluid comprising the altered particlesize cement kiln dust and introducing the treatment fluid into asubterranean formation. The cement kiln dust having a mean particle sizethat has been altered may be included in any of a number of welltreatment fluids that may be used in subterranean treatments, includingdrilling fluids, completion fluids, spacer fluids, stimulation fluids,and well clean-up fluids. For example, a drilling fluid may comprise thereduced particle size cement kiln dust, wherein the drilling fluid maybe circulated downwardly through a drill pipe and drill bit and thenupwardly through the well bore to the surface. The drilling fluid usedmay be any number of fluids (gaseous or liquid) and mixtures of fluidsand solids (such as solid suspensions, mixtures, and emulsions).

In some embodiments, a spacer fluid may comprise the cement kiln dusthaving a mean particle size that has been altered. Spacer fluids may beused, for example, in the displacement of fluids from well bore. In anembodiment, the fluid displaced by the spacer fluid comprises a drillingfluid. By way of example, the spacer fluid may be used to displace thedrilling fluid from the well bore. The drilling fluid may include, forexample, any number of fluids, such as solid suspensions, mixtures, andemulsions. Additional steps in embodiments of the method may compriseintroducing a pipe string into the well bore, introducing a cementcomposition into the well bore with the spacer fluid separating thecement composition and the first fluid. In an embodiment, the cementcomposition may be allowed to set in the well bore. The cementcomposition may include, for example, cement and water.

Accordingly, embodiments of the present invention disclose methods andcompositions that comprise cement kiln dust having a mean particle sizethat has been altered. There may be several potential advantages to themethods and compositions of the present invention, only some of whichmay be alluded to herein. One of the many potential advantages ofembodiments of the present invention is that reducing the particle sizeof the cement kiln dust can result in increased compressive strength forthe settable compositions after setting. For example, it has been shownthat compositions with reduced particle size cement kiln dust haveincreased compressive strength as compared to use of the cement kilndust prior to the size reduction. Another potential advantage is thataltering the mean particle size of the cement kiln dust may impact thegelation time of compositions containing the cement kiln dust. Yetanother potential advantage is that the mean particle size of the cementkiln dust may be selectively altered, for example, based on the size ofvoids. This could potentially result in more effective remedialcementing methods, as the particle size of the cement kiln dust has beenoptimized.

To facilitate a better understanding of the present invention, thefollowing examples of certain aspects of some embodiments are given. Inno way should the following examples be read to limit, or define, thescope of the invention.

Example 1

The following series of tests was performed to evaluate the forceresistance properties of settable compositions comprising cement kilndust having a mean particle size that has been reduced. Two differentsample settable compositions, designated Samples 1 and 2, were preparedby adding 250 grams of cement kiln dust to 267.3 grams of tap waterwhile mixing in a Waring blender at 4,000 rpm for 15 seconds followed bymixing at 12,000 rpm for 35 seconds for each sample. Sample 1 containedunground cement kiln dust while the cement kiln dust included in Sample2 was ground to a reduced particle size. Each of Samples 1 and 2 wasthen placed in a sealed cylindrical container, 2 inches in diameter by 4inches in height. Each container was placed in a water bath at 140° F.and allowed to cure for 96 hours. Each container was then removed fromthe water bath, allowed to cool, and the cylindrical samples weredemolded. The cylindrical samples were then placed in a Tinius Olsentester, and the compressive strengths were determined. The compressivestrength testing was performed in accordance with API RP Practice 10B-2,Recommended Practice for Testing Well Cements.

Sample 1 comprised water (106.93% bwoc) and cement kiln dust (100%bwoc). The cement kiln dust was unground and had a mean particle size ofabout 18.7 microns. Sample 1 had a density of 12 lb/gal.

Sample 2 comprised water (106.93% bwoc) and ground cement kiln dust(100% bwoc). The cement kiln dust in Sample 2 was ground from a meanparticle size of 18.7 microns to a mean particle size of 5.9 micronsusing an 8000 Mixer/Mill® ball mill, available from SPEX Sample Prep.Sample 2 had a mean particle size reduction of 68.45%. The cement kilndust was ground in the grinder for time period of about 30 minutes toabout 1 hour. Sample 2 had a density of 12 lb/gal.

The results of the compressive strength testing are provided in Table 1below. The data reported in the table below is the average of 3 testsfor each of the sample settable compositions.

TABLE 1 Compressive Strength Tests Sample Density Water CKD CKD ParticleTemp. 96-Hr Comp. No. (lb/gal) (% bwoc) (% bwoc) Size (micron) (° F.)Strength (psi) 1 12 106.93 100 18.7 140 64.3 2 12 106.93 100 5.9 140169.5

Example 1 thus indicates that reducing the particle size of the cementkiln dust may increase the compressive strength of the settablecompositions as compared to unground cement kiln dust. At 140° F., forexample, Sample 2 with cement kiln dust ground to a mean particle sizeof 5.9 microns had a 96-hour compressive strength of 169.5 psi ascompared to a 96-hour compressive strength of 64.3 psi for Sample 1 withunground cement kiln dust.

Example 2

An additional series of tests was performed to further evaluate theforce resistance properties of settable compositions comprising cementkiln dust have a mean particle size that has been reduced. Two differentsample settable compositions, designated Samples 3 and 4, were preparedby adding 200 gams of cement kiln dust to 213.9 grams of tap water whilemixing in a Waring blender at 4,000 rpm for 15 seconds followed bymixing at 12,000 rpm for 35 seconds for each sample. Sample 3 containedunground cement kiln dust while the cement kiln dust in Sample 4 wasground to a reduced particle. Each of the samples was then placed in anUltrasonic Cement Analyzer (“UCA”) from Farm Instruments, Houston, Tex.In the UCA, the compressive strength of each sample was determined overtime at 140° F. and 8,000 psi. The compressive strength testing wasperformed in accordance with API RP Practice 10B-2, Recommended Practicefor Testing Well Cements.

Sample 3 comprised water (106.93% bwoc) and cement kiln dust (100%bwoc). The cement kiln dust was unground and had a mean particle size ofabout 18.7 microns. Sample 3 had a density of 12 lb/gal.

Sample 4 comprised water (106.93% bwoc) and ground cement kiln dust(100% bwoc). The cement kiln dust in Sample 4 was ground from a meanparticle size of 18.7 microns to a mean particle size of 9.7 micronsusing an 8000 Mixer/Mill® ball mill, available from SPEX Sample Prep.Sample 4 had a mean particle size reduction of 48.13%. The cement kilndust was ground in the grinder for time period of about 30 minutes toabout 1 hour. Sample 4 had a density of 12 lb/gal.

The results of the compressive strength testing are provided in Table 2below. The data reported in the table below is compressive strengthsreported by the UCA at 12 hours and 24 hours.

TABLE 2 UCA Compressive Strength Tests Sample Density Water CKD CKDParticle Temp. 12-Hr Comp. 24-Hr Comp. No. (lb/gal) (% bwoc) (% bwoc)Size (micron) (° F.) Strength (psi) Strength (psi) 3 12 106.93 100 18.7140 153 166 4 12 106.93 100 9.7 140 298 326

Example 2 thus indicates that reducing the particle size of the cementkiln dust may increase the compressive strength of the settablecompositions as compared to unground cement kiln dust. At 140° F., forexample, Sample 4 with cement kiln dust ground to a mean particle sizeof 9.7 microns had a 12-hour compressive strength of 298 psi as comparedto a 12-hour compressive strength of 153 psi for Sample 3 with ungroundcement kiln dust.

It should be understood that the compositions and methods are describedin terms of “comprising,” “containing,” or “including” variouscomponents or steps, the compositions and methods can also “consistessentially of” or “consist of” the various components and steps.Moreover, the indefinite articles “a” or “an,” as used in the claims,are defined herein to mean one or more than one of the element that itintroduces.

For the sake of brevity, only certain ranges are explicitly disclosedherein. However, ranges from any lower limit may be combined with anyupper limit to recite a range not explicitly recited, as well as, rangesfrom any lower limit may be combined with any other lower limit torecite a range not explicitly recited, in the same way, ranges from anyupper limit may be combined with any other upper limit to recite a rangenot explicitly recited. Additionally, whenever a numerical range with alower limit and an upper limit is disclosed, any number and any includedrange falling within the range is specifically disclosed. In particular,every range of values (of the form, “from about a to about b,” or,equivalently, “from approximately a to b,” or, equivalently, “fromapproximately a-b”) disclosed herein is to be understood to set forthevery number and range encompassed within the broader range of valueseven if not explicitly recite. Thus, every point or individual value mayserve as its own lower or upper limit combined with any other point orindividual value or any other lower or upper limit, to recite a rangenot explicitly recited.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Although individual embodiments arediscussed, the invention covers all combinations of all thoseembodiments. Furthermore, no limitations are intended to the details ofconstruction or design herein shown, other than as described in theclaims below. Also, the terms in the claims have their plain, ordinarymeaning unless otherwise explicitly and clearly defined by the patentee.It is therefore evident that the particular illustrative embodimentsdisclosed above may be altered or modified and all such variations areconsidered within the scope and spirit of the present invention. Ifthere is any conflict in the usages of a word or term in thisspecification and one or more patent(s) or other documents that may beincorporated herein by reference, the definitions that are consistentwith this specification should be adopted.

1. A method of preparing cement kiln dust comprising: providing cement kiln dust having an original particle size; and altering the mean particle size of the cement kiln dust from the original size by grinding, separating, or a combination thereof.
 2. The method of claim 1 wherein the mean particle size of the cement kiln dust is altered to at least 5% greater than its original size.
 3. The method of claim 1 wherein the mean particle size of the cement kiln dust is altered to at least 5% less than its original size.
 4. The method of claim 1 wherein the mean particle size of the cement kiln dust is altered to a range of from about 1 micron to about 350 microns.
 5. The method of claim 1 wherein the altering the mean particle size comprises grinding the cement kiln dust.
 6. The method of claim 1 wherein the altering the mean particle size comprises intergrinding the cement kiln dust with one or more additives to a mean particle size in a range of from about 1 micron to about 350 microns.
 7. The method of claim 6 wherein the one or more additives comprise at least one additive selected from the group consisting of hydraulic cement, fly ash, slag, shale, zeolite, metakaolin, pumice, perlite, lime, silica, rice-hull ash, micro-fine cement, lime kiln dust, and any combination thereof.
 8. A well treatment fluid comprising: cement kiln dust having a mean particle size that has been altered from its original size by grinding, separating, or a combination thereof; and water.
 9. The well treatment fluid of claim 8 wherein the mean particle size of the cement kiln dust is altered to at least 5% greater than its original size.
 10. The well treatment fluid of claim 8 wherein the mean particle size of the cement kiln dust is altered to at least 5% less than its original size.
 11. The well treatment fluid of claim 8 wherein the mean particle size of the cement kiln dust is in a range of from about 1 micron to about 350 microns.
 12. The well treatment fluid of claim 8 wherein the mean particle size of the cement kiln dust is less than about 15 microns.
 13. The well treatment fluid of claim 8 wherein the mean particle size of the cement kiln dust is in a range of from about 5% to about 95% of its original size.
 14. The well treatment fluid of claim 8 wherein the mean particle size of the cement kiln dust has been reduced.
 15. The well treatment fluid of claim 8 wherein the treatment fluid comprises a fluid selected from the group consisting of a drilling fluid, a completion fluid, a spacer fluid, a stimulation fluid, a well clean up fluid, and any combination thereof.
 16. The well treatment fluid of claim 8 wherein the treatment fluid is a settable composition.
 17. The well treatment fluid of claim 16 wherein the mean particle size of the cement kiln dust has been reduced in an amount sufficient to provide an increase in 24-hour compressive strength of at least about 5% as measured using an Ultrasonic Cement Analyzer while maintained at 140° F. and 3,000 psi.
 18. The well treatment fluid of claim 16 wherein the mean particle size of the cement kiln dust has been reduced in an amount sufficient to provide an increase in 24-hour compressive strength of at least about 50% as measured using an Ultrasonic Cement Analyzer while maintained at 140° F. and 3,000 psi.
 19. The well treatment fluid of claim 16 wherein the cement kiln dust is present in the settable composition in an amount in a range of from about 1% to 100% by weight of cementitious components in the settable composition.
 20. The well treatment fluid of claim 16 wherein the cement kiln dust is present in the settable composition in an amount in a range of from about 1% to 100% by weight of cementitious components in the settable composition.
 21. The well treatment fluid of claim 16 wherein the cement kiln dust is present in the settable composition in an amount in a range of from about 1% to about 50% by weight of cementitious components in the settable composition.
 22. The well treatment fluid of claim 16 wherein the cement kiln dust is present in the settable composition in an amount in a range of from about 50% to 100% by weight of cementitious components in the settable composition.
 23. The well treatment fluid of claim 16 wherein the cement kiln dust was prepared by a process comprising intergrinding the cement kiln dust with an additional additive to a mean particle size in a range of from about 1 micron to about 350 microns.
 24. The well treatment fluid of claim 23 wherein the additional additive comprises an additive selected from the group consisting of hydraulic cement, fly ash, slag, shale, zeolite, metakaolin, pumice, perlite, lime, lime kiln dust, silica, rice-hull ash, micro-fine cement, and any combination thereof.
 25. The well treatment fluid of claim 16 wherein the water is present in an amount sufficient to form a pumpable slurry.
 26. The well treatment fluid of claim 16 wherein the settable composition further comprises an additive selected from the group consisting of a set retarding additive, a strength-retrogression additive, a set accelerator, a weighting agent, a lightweight additive, a gas-generating additive, a mechanical-property-enhancing additive, a lost-circulation material, a filtration-control additive, a dispersant, a fluid-loss-control additive, a defoaming agent, a foaming agent, an oil-swellable particle, a water-swellable particle, a thixotropic additive, and any combination thereof.
 27. The well treatment fluid of claim 16 wherein the settable composition further comprises an additive selected from the group consisting of hydraulic cement, fly ash, slag, shale, zeolite, metakaolin, pumice, perlite, lime, lime kiln dust, silica, rice-hull ash, micro-fine cement, a salt, a fiber, a hydratable clay, a microsphere, an elastomer, an elastomeric particle, a resin, a latex, and any combination thereof.
 28. An additive for a settable composition comprising: cement kiln dust having a mean particle size that has been altered from its original size by grinding, separating, or a combination thereof.
 29. The additive of claim 28 wherein the mean particle size of the cement kiln dust has been altered to at least 5% greater than its original size.
 30. The additive of claim 28 wherein the mean particle size of the cement kiln dust has been altered to at least 5% less than its original size.
 31. The additive of claim 28 wherein the mean particle size of the cement kiln dust is in a range of from about 1 micron to about 350 microns.
 32. The additive of claim 28 wherein the mean particle size of the cement kiln dust is less than about 15 microns.
 33. The additive of claim 28 wherein the mean particle size of the cement kiln dust is in a range of from about 5% to about 95% of its original size. 